Malkin and Kessel had 0 goals and 1 point in the 4 losses to Washington last year, and 3 of those 4 losses were by 1 goal. Murray 100% played well enough for the team to win that series, the Penguins lost in the playoffs last year because they couldn't score. In the playoffs, goals against matter way more than save%. If you're expecting Murray to give up 2 or fewer goals every game or you're going to lose, it's not on the goalie if you do lose.
The 2016 defense was better as a group, but I don't think it was better on paper. If this team was as committed to playing team defense as the 2016 team was, I don't think the results now would be worse than the results in 2016. Let's just say Dumoulin, Maatta and Letang are a wash (although Dumoulin and Letang are better now than they were in 2016 IMO), you have Schultz, Pettersson, Johnson, Riikola and Ruhwedel vs Daley, Cole, Lovejoy, reclamation project Schultz and Pouliot. I'd take Pettersson and Schultz over Daley and Cole, and at that point, having Lovejoy vs Johnson doesn't really matter.
The only black eye on this defense is Jack Johnson, this defense would be perfect on paper if they just had a right handed Cole on the bottom pair with Pettersson/Maatta.